1. Field of the Invention
The invention is concerned with synthetic ester lubricants. More particularly, it deals with synthetic ester lubricants containing a free hydroxyl, which ester lubricant is preferably combined with a synthetic hydrocarbon lubricating oil.
2. Discussion of the Prior Art
For several years there have been numerous efforts to reduce the amount of fuel consumed by automobile engines and the like. The search for ways to do this was given added impetus by the oil embargo. Many of the solutions have been strictly mechanical, as for example, setting the engine for a leaner burn or simply building smaller cars and smaller engines.
Other efforts have revolved around finding lubricants that reduce the overall friction in the engine, thus allowing a reduction in energy requirements thereto. A considerable amount of work has been done with mineral lubricating oils and greases, modifying them with additives to reduce their friction properties. On the other hand, new lubricants have been synthesized and compounded for use in modern engines. Among these is Mobil 1, a synthetic fluid which is known to reduce fuel consumption by a significant amount.
So far as is known, no effort has been made to employ hydroxyl-containing acid esters as a lubricant per se. U.S. Pat. No. 2,788,326 discloses some of the esters suitable for the present invention, e.g. glycerol monooleate, as minor components of lubricating oil compositions. U.S. Pat. No. 3,235,498 discloses, among others, the same ester as just mentioned, as an additive to other oils. U.S. Pat. No. 2,443,578 teaches esters wherein the free hydroxyl is found in the acid portion, as for example in tartaric acid.
It will be noted that the above patents, as well as numerous others, are directed to the use of such esters as additives. Other patents, such as U.S. Pat. Nos. 2,798,083; 2,820,014; 3,115,519; 3,282,971; and 3,309,318 as well as an article by R. S. Barnes et al. entitled "Synthetic Ester Lubricants" in Lubrication Engineering, August, 1957, pp. 454-457, teach lubricants prepared from polyhydric alcohols and acid containing no hydroxyl other than those associated with the acid function. However, all these references teach lubricants prepared from the fully esterified material.